The art of single nostril breathing

Single nostril breathing (digital pranayama, according to Mr. guru Iyengar) is a great way for balancing.  Most people associate it with yoga practice.  Actually it is also part of Buddhist and Taoist practice.  It is about balancing.  As with everything else on mind-body practice, it is first applied to the body and with mindful attention, bodily change, together with some (optional) belief system, like the Yogi's Sun to signify the left nostril and Moon to signify the right nostril. Believe system is good if it is considered as "suspension of disbelief", and is quite unnecessary when it goes into the realm of superstition.

Question: What is the use of single nostril breathing when air goes into the same lungs?

Valid question, the act of single nostril breathing will be quite useless if practice logic is not being understood.

In brief, the art of single nostril breathing is like this:

1. Close one nose with a finger or thumb of the same side
2. The engaged hand will be "earthed" and will not act as chi generator
3. The hand of the non-engaged side will be stretched
4. Chi will flow only on the non-engaged side
5. The channel of chi flow will be determined by objective of that particular training session [such as central (non-engaged side) channel opening or shoulder joint/shoulder blade (non-engaged side) opening]
6. Doing alternative single nostril breathing will enable a practitioner to gauge the difference between his two sides and can therefore direct his training accordingly
   

Single nostril breathing